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Expect the 10 candidates participating in the third Republican presidential debate to highlight rising tensions in the unsettled field.

Political outsiders Donald Trump and Ben Carson are the front-runners in national polls, and they may take aim one another during the 8 p.m. EDT debate in Boulder, Colorado, being aired on CNBC. But the anticipated sparring among the experienced politicians in the race could prove just as intense, given the dwindling time for them to stand out in the crowded contest.

Jeb Bush's standing in the race has never been weaker. The former Florida governor is the son and brother of presidents. Because of his overwhelming financial advantage, he was considered the front-runner for several months, even when he started to lag in the polls. But his campaign showed signs of financial distress last week by announcing a big payroll cut. The internal problems shined new light on Bush's liabilities, including underwhelming showings as a campaigner. He needs to have a strong night to help reassure nervous supporters that he has the strength to survive a suddenly uphill battle.

No one is better positioned to benefit from Bush's struggles than his Florida protege, Marco Rubio. Especially after Wisconsin Gov. Scott Walker quit the race, the 44-year-old first-term senator is considered one of the few candidates who can bridge the GOP's warring factions by appealing to establishment and hard-line wings. Bush's team has identified Rubio as its greatest threat. The two may be longtime friends, but expect Bush to go on the attack. Rubio has largely avoided getting dragged into the back-and-forth so far. He may have no option Wednesday night.

Carson, a retired neurosurgeon, may be one of the least known candidates despite his top-of-the-pack polling. After playing bit parts in the first two debates, Carson has become a higher priority for his rivals, particularly those chasing the antiestablishment vote. None has gone after Carson more aggressively than billionaire businessman Donald Trump, who has questioned Carson's energy, policies and religion. The soft-spoken Carson has refused to counterattack, but expect him to defend himself and explain his positions in the face of mounting pressure. His aides also hope he will tone down the rhetoric; during the campaign he's made references to Nazis and slavery.

Only in the past week or two has Trump shown signs of vulnerability, but the showman is the ultimate wild card on the debate stage. He has shown a willingness to say or do virtually anything on national television, and heading into the debate, he has jabbed at just about every challenger — none more so than Carson. Based on the ratings in previous debates, people are drawn to the Trump show, but are they growing tired of his act?

New Jersey Gov. Chris Christie was a political powerhouse not long ago. Kentucky Sen. Rand Paul was among the most interesting figures in politics. Texas Sen. Ted Cruz was a champion college debater. Former technology executive Carly Fiorina was an earlier debate winner. Yet all came into Wednesday night's round as supporting actors. With 10 candidates on the stage for two hours, there simply won't be enough time for everyone to stand out — and some of them need to.